Guignon,
The CAS settings on the two boards may be different
and if the kx133 bus is asynchronous this would add
a one cycle latency delay to any memory reference.
This reduces throughput across memory reference bursts.
A good reference on this issue (if it applies here)
is at:
http://www.aceshardware.com/Spades/read.php?article_id=5000172
rbw